IEC TS 62715-5-4:2019

IEC TS 62715-5-4 ®
Edition 1.0 2019-05
TECHNICAL
SPECIFICATION
colour
inside
Flexible display devices –
Part 5-4: Measuring method of blur in flexible transparent displays
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IEC TS 62715-5-4 ®
Edition 1.0 2019-05
TECHNICAL
SPECIFICATION
colour
inside
Flexible display devices –
Part 5-4: Measuring method of blur in flexible transparent displays

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 31.120 ISBN 978-2-8322-6928-2

– 2 – IEC TS 62715-5-4:2019  IEC 2019
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references . 5
3 Terms, definitions and abbreviated terms . 5
3.1 Terms and definitions . 5
3.2 Abbreviated terms . 5
4 Measuring conditions . 6
4.1 Standard measuring environmental conditions . 6
4.2 Standard darkroom conditions . 6
4.3 Standard setup conditions . 6
4.3.1 Display mounting . 6
4.3.2 Measuring configuration . 6
4.3.3 Starting conditions of measurements . 7
4.3.4 Conditions of measuring equipment . 7
5 Blur caused by a flexible transparent display . 8
5.1 Purpose . 8
5.2 Measuring conditions . 9
5.3 Measuring method . 9
Annex A (informative) Example of blur measurement configuration . 13
A.1 Purpose . 13
A.2 Examples of parameters in blur measurement . 13
Bibliography . 16

Figure 1 – Geometric configuration of measuring system . 7
Figure 2 – Layout diagram of measurement setup . 8
Figure 3 – Examples of test pattern with and without blur and luminance
measurements . 9
Figure 4 – Schematic diagram to illustrate the method of calculating the standard
deviation specifying the Gaussian blur model . 11
Figure A.1 – Examples of different levels of blur . 13

Table 1 – Example of test report for blur measure . 12
Table A.1 – Examples of the maximum measurement field diameter for different
values of blur width . 14
Table A.2 – Examples of the maximum measurement field diameter for different
values of blur width . 14
Table A.3 – Examples of PPI for different configurations of a reference display device . 14
Table A.4 – Examples of combinations of measurement field diameter and
corresponding distance from the LMD to the reference display device yielding a
measurement field angle of 1° . 15

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
FLEXIBLE DISPLAY DEVICES –
Part 5-4: Measuring method of blur in flexible transparent displays

FOREWORD
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• the required support cannot be obtained for the publication of an International Standard,
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• the subject is still under technical development or where, for any other reason, there is the
future but no immediate possibility of an agreement on an International Standard.
Technical specifications are subject to review within three years of publication to decide
whether they can be transformed into International Standards.
IEC TS 62715-5-4, which is a technical specification, has been prepared by IEC technical
committee 110: Electronic displays.

– 4 – IEC TS 62715-5-4:2019  IEC 2019
The text of this technical specification is based on the following documents:
Enquiry draft Report on voting
110/1055/DTS 110/1084/RVTDS
Full information on the voting for the approval of this technical specification can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 62715 series, published under the general title Flexible display
devices, can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.

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FLEXIBLE DISPLAY DEVICES –
Part 5-4: Measuring method of blur in flexible transparent displays

1 Scope
This part of IEC 62715 specifies the measuring conditions and measuring methods for
determining the blur of objects when viewed through a flexible transparent display. This
document mainly applies to flexible transparent display modules that have a constant radius
curvature about a single axis. The display is measured in a static mechanical state.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements of this document. For dated references, only the edition
cited applies. For undated references, the latest edition of the referenced document (including
any amendments) applies.
IEC 62715-1-1, Flexible display devices – Part 1-1: Terminology and letter symbols
IEC 62715-5-1, Flexible display devices – Part 5-1: Measuring methods of optical
performance
3 Terms, definitions and abbreviated terms
For the purposes of this part of IEC 62715, the terms and definitions in IEC 62715-1-1 and the
following apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1 Terms and definitions
3.1.1
blur
unclear or indistinct outline of objects when they are viewed through a flexible transparent
display
3.1.2
through-screen properties
image quality attributes when the intended information is behind the display panel and is
viewed through it
3.1.3
pixel
smallest element of a picture that can be distinguished from its neighbouring elements
3.2 Abbreviated terms
DUT device under test
LMD light measuring device
PPI  pixels per inch
– 6 – IEC TS 62715-5-4:2019  IEC 2019
4 Measuring conditions
4.1 Standard measuring environmental conditions
Measurements shall be carried out under the standard environmental conditions:
• temperature: 25 °C ± 3 °C,
• relative humidity: 25 % to 85 %,
• atmospheric pressure: 86 kPa to 106 kPa.
When different environmental conditions are used, they shall be noted in the test report.
4.2 Standard darkroom conditions
The luminance contribution from unwanted background illumination reflected off and/or
transmitted through the DUT shall be less than 1/20 of the DUT’s black state luminance. If this
condition is not satisfied, then background subtraction is required and it shall be noted in the
test report. In addition, if the sensitivity of the LMD is inadequate to measure at these low
levels, then the lower limit of the LMD shall be noted in the test report.
4.3 Standard setup conditions
4.3.1 Display mounting
The fixture used to mount a curved display plays a critical role in obtaining accurate and
reproducible results.[1] The display mount should be designed to accommodate the specific
bendable characteristics of the flexible transparent display in its intended use configuration.
The mount should be capable of maintaining the intended shape of the display and locate it in
the required measurement position and viewing direction. The measuring methods specified in
this document only apply for displays that have a constant radius of curvature about a single
axis.
The origin of the coordinate system is positioned at the imaging surface of the DUT and
centered on the screen. Unless otherwise specified, the optical axis of the LMD shall be
aligned to within 1° of the DUT’s surface normal at its centre. For spot-type LMDs, the retro-
reflection of the LMD can be used to obtain this alignment. Otherwise, an alignment laser can
be used to define the optical axis. The methods also assume that the rotation stages and
mechanical mounting have sufficient accuracy and stability to maintain a tolerance of less
than 1°.
4.3.2 Measuring configuration
Figure 1 illustrates the geometric configuration of the DUT, reference display device and LMD.
The DUT is located in its intended use configuration using the display mounting fixture. It is
positioned so that the optical axis of the LMD shall be aligned to within 1° of the DUT’s
surface normal at its centre. The purpose of the reference display device is to display a test
pattern. A flat display can be used as a reference display device. It is positioned to be parallel
to the DUT’s surface normal at the centre. In Figure 1, the distance from the DUT to the
reference display device is denoted as background distance. Background distance can be
determined for convenience of measurement and based on the intended applications of the
DUT. The LMD shall be focused on the test pattern.
—————————
Numbers in square brackets refer to the Bibliography.

Figure 1 – Geometric configuration of measuring system
4.3.3 Starting conditions of measurements
Measurements shall be started after the DUT, reference display device and the LMD achieve
stability. It is recommended that when the display is first turned on, it should be operated for
at least 30 min. Sufficient warm-up time has to be allowed for both the DUT and reference
display device to reach a luminance stability level of less than ± 3 % over the entire
measurement.
4.3.4 Conditions of measuring equipment
The general conditions of the measuring equipment specified in IEC 62715-5-1 are adopted.
Light measurements shall generally be measured in terms of photometric or colorimetric units
for a CIE 1931 standard colorimetric observer [2]. Illuminance incident on the DUT can be
measured by a photometer. The LMD shall be a luminance meter, colorimeter, or a
spectroradiometer. An imaging LMD can be used for two-dimensional measurements of
transmitted luminance to eliminate the need for translational motions. When a two-
dimensional LMD is used for measurement, efforts shall be made so that the measurement
results of the two-dimensional LMD are equal to those of the spot-type LMD. A moiré pattern
from interference between the pixel patterns of the DUT and LMD can be prevented by
focusing the LMD on the test target. If the test target is displayed on a reference display, a
moiré pattern from interference between the pixel patterns of the reference display and the
LMD can be prevented by using a reference display of high resolution (a
...